This application claims the priority of German patent document 100 57 798.9, filed Nov. 22, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a motor vehicle drive which includes an internal combustion engine and at least one electric starter motor.
In a motor vehicle drive of this type disclosed in German Patent Document DE 196 32 074 A1, a starter generator, which has a rotor constructed as a flywheel, can be coupled with an internal-combustion engine in order to start it. After the start, the starter generator functions as a dynamo or a generator, for charging an electric battery. The generator may be driven from either the forward or the rearward end of the crankshaft of the internal-combustion engine.
German Registered Utility Model DE 94 22 162 U1 shows a motor vehicle hybrid drive with a series connection consisting of an internal-combustion engine, a first clutch, a transmission, a second clutch and a vehicle axle. Between the two clutches, an electric machine is connected in a drive relationship with the transmission. The electric machine can be operated as an electric motor, as a generator, as an electromagnetic brake and as a starter for starting the internal-combustion engine. For generating current at low vehicle speeds of, for example, from 0 to 50 km/h, where the internal-combustion engine is not used to propel the motor vehicle, an additional generator is required which is driven by the crankshaft of the internal-combustion engine.
German Patent Document DE 29 43 554 A1 shows a motor vehicle hybrid drive having an electric machine which can be supplied with electric energy from an electric energy accumulator or feeds electric energy back into the energy accumulator. The electric machine is connected with a driving axle of a motor vehicle via a first separating clutch and with an internal-combustion engine arranged in series therewith, via a second separating clutch. According to the requirement, only one of two or both separating clutches are opened or closed.
European Patent Document EP 0 649 769 A1 shows a driving device which can be connected to an external power supply system for transport devices, such as a trolley bus or a streetcar with an external power supply by an overhead line, or a railroad with an external electric power supply. The driving device contains an electric travelling device motor which can be supplied with current alternatively by an external power supply system or by a generator present in the vehicle, which generator can be driven by an internal-combustion engine. With respect to the drive, the generator is mechanically constantly connected with auxiliaries.
Drives in which energy for propulsion is generated by an internal-combustion engine and by at least one electric motor are generally called xe2x80x9chybrid drivesxe2x80x9d. This invention also is such a hybrid drive.
One object of the invention is to construct a hybrid motor vehicle drive which is structurally simple.
Another object of the invention is to provide such a hybrid drive which has a low weight.
Still another object of the invention is to provide such a hybrid drive which consumes less energy.
These and other objects and advantages are achieved by the motor vehicle hybrid drive according to the invention, which includes an internal-combustion engine and at least one electric machine which can be operated as a starter for starting the internal-combustion engine or as a generator. The electric machine can be uncoupled from the internal-combustion engine or can be connected in a drive relationship with it, via a first clutch; and an auxiliary equipment drive path is provided from the electric machine to drive at least one auxiliary device (such as an air conditioner compressor, a hydraulic or electric drive for a cable winch, or other similar devices on the vehicle).
This configuration has the advantage that the electric machine can operate as a motor and can drive the auxiliary equipment when the internal-combustion engine is switched off. Alternatively, when the internal-combustion engine is switched on, it can drive the electric machine for generating power for charging a power accumulator.
According to a preferred embodiment, the auxiliary equipment driving path contains a second clutch which can connect the at least one auxiliary device in a drive relationship with the electric machine, or can separate it from the electric machine.
This feature has the advantage that auxiliary devices which require a particularly large amount of driving power can be uncoupled from the electric machine and from the internal-combustion engine. On the other hand, when the electric machine operates as a starter motor, it can be used for starting the internal-combustion engine; and when the electric machine drives the motor vehicle, in addition to or without the switched-on internal-combustion engine (for example, when the internal-combustion engine is switched off, in the low vehicle speed range between 0 km/h and 50 km/h, or when the internal-combustion engine is switched on, in addition to the latter), it supplies propulsive power in driving situations in which a particularly large amount of driving power is required (for example, during a passing maneuver or on a particularly steep hill). Auxiliary devices which require significantly more driving power than other auxiliary devices are, for example, refrigerant compressors for a motor vehicle air-conditioning system or hydraulic or electric drives for a cable winch or other working apparatuses provided on the motor vehicle. In addition, the uncoupling of one or more devices has the advantage that the electric machine can be smaller, providing a smaller output which is sufficient for starting the internal-combustion engine or for supplying vehicle driving energy in addition to or as an alternative to the internal-combustion engine.
A motor vehicle normally also contains other auxiliary equipment, such as a water pump or an oil pump, which require significantly less driving energy than, for example, a refrigerant compressor for compressing refrigerant of an air-conditioning system. Such auxiliary devices, which require relatively little driving energy, according to the invention can be connected to be driven by the rotor of the electric machine, so that they can be uncoupled or, according to another embodiment, so that they cannot be uncoupled.
According to another preferred embodiment of the invention, the auxiliary-aggregate driving path has two or more driving branches which have different transmission ratios. One or more auxiliary devices are connected to only one driving branch or can be connected in an optionally changeable manner with one or the other driving branch, and as a result can be connected at different driving ratios with the electric machine.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.